This invention relates to automatic reproducing apparatus and to the frames, structure and covers used in such apparatus. In particular, the present invention relates to a machine frame structure which simplifies the construction of the paper path.
Historically in the manufacture of automatic reproducing machines, the construction initially was based on a main frame comprising one or more large die castings of aluminum or the like to which operational subassemblies such as a developer housing, cleaner housing or copy sheet transport would be mounted. Often times the subassemblies themselves were built on a small die cast frame members to which each of individual subassembly parts had to be fixed. Some machines, in large part, consisted of massive frames and subframe structures to which the individual operational elements were directly mounted or mounted through brackets. Typical of commercial products of this nature were the Xerox 914 and 3600 model copiers. The Xerox 3600 model is exemplified in U.S. Pat. No. 3,301,126 to Osborne et al.
The next step in the development of the frame structure was the use of sheet metal as the principle frame structures. Although some die castings were still used for mounting subassemblies, a rapid switch to the use of sheet metal and steel bracketing replaced the high level use of metal die castings. However the individual operational parts of the machine continued to be assembled first as a subassembly which was mounted to the main frame. Exemplary of this type of copier construction is the Xerox 4000 copier.
A later development in automatic reproducing machine construction was the use of a unitized type of construction which uses a sheet metal frame with as many of the individual operational elements being mounted directly to it. In this type of construction, the use of subassemblies is to a very large degree replaced by mounting the individual elements directly to the sheet metal frame. This type of construction is exemplified by that found in the Xerox 3300 copier. A variant of this type of construction uses straight pieces of sheet metal with punched and machined holes for mounting supporting brackets and machine elements.
In all these techniques, a very large number of suitable brackets, holders or subassembly frames are required to hold or mount every single piece of the entire operational structure of the machine onto the frame assembly. The number of parts including mounting blocks, brackets and fasteners is very large. In addition, it is necessary to drill or tap several suitable mounting holes in the frame and subframe structures. Further and perhaps most important from an operational sense, every mounted element or assembly must be adjusted for operational tolerances relative to its frame structure as well as relative to the other operational elements or assemblies with which it interacts. For example, the developer assembly, charging corotron assembly and cleaning assembly must all be aligned and adjusted for operational tolerances with the photoconductor drum. It also frequently happens that these adjustments become loose with time and use and must be continuously aligned for maximum operational efficiency and copying quality. In addition the assembly costs to put all these parts together and adjust them increases to a very high degree as the number of parts and complexity of adjustment increases. Simply said, it cost more to install every single screw in a machine.
Traditionally one of the operational aspects of automatic reproducing machines over which a great degree of control and precision adjustment is required is with regard to the paper supply to the copy output station. Typically, these paths have been defined by separate paper transports made from sheet metal with belt or roller drives for different parts of the machine and by baffles, gates, stops, etc., all separately mounted to the machine main frame or selected sub-assemblies. Representative of this type of construction is the paper path shown in U.S. Pat. No. 3,301,126 to Osborne et al which in FIG. 2 illustrates separate paper transports from the supply to the drum, from the drum to the fuser and from the fuser to the output station. In addition to these principal transport assemblies, a number of baffles, gates and brackets are used to guide or direct the copy sheet through its path. If any one of these elements which are mounted to its main frame or smaller subassemblies becomes misaligned there is the possibility of a paper jam or damage to paper occurring. The probability of this happening of course increases with the number of elements that must be mechanically aligned or adjusted in the machine. If some element comes out of adjustment, it may even require that use of the reproducing machine be discontinued until a trained technician can readjust the element to its proper position which detracts from overall reliability and user satisfaction.